/**
 * Copyright (c) Microsoft Corporation
 * 
 * All rights reserved. 
 * 
 * MIT License
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files 
 * (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, 
 * publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, 
 * subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED *AS IS*, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR 
 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH 
 * THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.JavaSparkContext;
import org.apache.spark.api.java.function.Function;
import org.apache.spark.api.java.function.Function2;

import java.util.ArrayList;
import java.util.List;

/**
 * Computes an approximation to pi
 * Usage: JavaSparkPi [slices]
 * This is adapted from Apache Spark GitHub: https://github.com/apache/spark/blob/master/examples/src/main/java/org/apache/spark/examples/JavaSparkPi.java
 */
public final class JavaSparkPi {

    public static void main(String[] args) throws Exception {
        //use this line if you want to run your application in the cluster
        //SparkConf sparkConf = new SparkConf().setAppName("JavaSparkPi");
        SparkConf sparkConf = new SparkConf().setAppName("JavaSparkPi").setMaster("local[2]");
        JavaSparkContext jsc = new JavaSparkContext(sparkConf);

        int slices = (args.length == 1) ? Integer.parseInt(args[0]) : 2;
        int n = 100000 * slices;
        List<Integer> l = new ArrayList<Integer>(n);
        for (int i = 0; i < n; i++) {
            l.add(i);
        }

        JavaRDD<Integer> dataSet = jsc.parallelize(l, slices);

        int count = dataSet.map(new Function<Integer, Integer>() {
            @Override
            public Integer call(Integer integer) {
                double x = Math.random() * 2 - 1;
                double y = Math.random() * 2 - 1;
                return (x * x + y * y < 1) ? 1 : 0;
            }
        }).reduce(new Function2<Integer, Integer, Integer>() {
            @Override
            public Integer call(Integer integer, Integer integer2) {
                return integer + integer2;
            }
        });

        System.out.println("Pi is roughly " + 4.0 * count / n);

        jsc.stop();
    }
}